The place of plastics in the automotive industry has grown tremendously as it is the key to future high performance, more fuel efficient vehicles. Plastics offer designers and engineers multiple advantages in many applications by providing lightweight and versatile designs as well as lower manufacturing costs. The versatility of plastics can be expressed by the wide range of shapes and surfaces finishes now possible. However, this versatility would not be possible without quality plastic injection mold steels. The increasing demand for fuel efficient cars is pushing designers to create more aerodynamic cars, which in turn require larger complex plastic parts such as bumpers, dashboards and door panels. Other industries have similar requirements for plastic parts such as exterior furniture. Plastic injection molding is used for a fast paced production and tool steels are used for this application. The properties of a quality plastic injection mold steel vary from the mold manufacturer to the end-user. Good machinability as well as the ability to provide a good surface finish are important aspects for the mold manufacturer. However, uniform hardness is the key for the end-user to produce parts without shape distortion. As parts increase in size, molds have to be larger and still display these properties across the entire section.